Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$241.46	10.206%	$266.1034	$266.10	$266.10	$266.10
Purchase #2	$45.51	4.602%	$47.6044	$47.60	$47.60	$47.60
Purchase #3	$246.82	11.108%	$274.2368	$274.24	$274.25	$274.20
Purchase #4	$39.72	7.729%	$42.79	$42.79	$42.80	$42.80
Purchase #5	$244.67	10.736%	$270.9378	$270.94	$270.95	$270.90
Purchase #6	$122.44	7.311%	$131.3916	$131.39	$131.40	$131.40
Purchase #7	$97.32	7.718%	$104.8312	$104.83	$104.85	$104.80
7 purchase totals =	$1,037.94		$1,137.8952	$1,137.89	$1,137.95	$1,137.80